Fertility fears hit Atkins diet

Would-be mothers who follow the Atkins diet may be reducing their chances of having a baby, warn researchers.

Female mice fed a high-protein diet before conception are less likely to produce live offspring, scientists told the European Society for Human Reproduction and Embryology meeting in Berlin this week. "The data indicate that a high-protein diet is not advisable while trying to conceive," says David Gardner from the Colorado Center for Reproductive Medicine, who led the study.

Devotees of Atkins' regime follow a high-protein, low-carbohydrate diet in the hope of shedding pounds. At certain points, followers may consume a diet containing up to 25% protein; that is around 10% more than people usually eat.

Gardner's team fed their mice diets containing either 25% or 14% protein for one month, then allowed them to mate. The researchers transferred the resulting 174 embryos into the wombs of surrogate mothers in order to test specifically how maternal diet before conception affects embryo health.

Only 65% of the embryos in the high-protein group developed into fetuses compared with 81% in the standard-protein group. Embryos conceived by 'high protein' animals were also more likely to spontaneously abort later in pregnancy: 16% of 'high protein' fetuses were miscarried, compared with just 1% of controls.

Rodents and humans are very different, cautions Catherine Collins, spokeswoman for the British Dietetic Association, so it is difficult to extrapolate from mouse to man. "But it is possible that high-protein diets have long-term effects on fertility," she says. Opponents of the Atkins diet claim that the nutritional programme can lead to metabolic problems, mood disorders and gout.

Gardner believes that high-protein diets may affect fertility by altering the genetic profile of the developing embryo. As proteins are broken down, levels of ammonium go up. Females on high protein diets have three times more ammonium in their reproductive tracts than animals on normal diets. In turn, this may affect imprinting, the process by which cells turn specific copies of parental genes on and off.

As expected, over 60% of embryos from 'high protein' mothers show defects in imprinting compared with 30% of control embryos. One growth-related gene, called H19, was adversely affected. This may explain the embryos' poor growth, says Gardner.